This invention relates generally to a movement for a timepiece with a stepping motor and more particularly relates to a three hand low cost movement for a quartz analog wristwatch.
Quartz analog wristwatches are known which have a Lavet-type stepping motor energized by periodic current pulses provided by an integrated circuit, which is energized by a button-type energy cell contained in the timepiece movement. The stepping motor, which is most commonly in use, has a stator including a core and a winding connected to receive the current Pulses which alternate in polarity. The rotor of the stepping motor most commonly has a two pole permanent magnet rotatable within an opening in the stator, so that with each pulse, the rotor steps one half a revolution. The rotor has an output gear pinion which rotates the hands of the timepiece through a suitable gear reduction train. The present invention concerns an improvement and simplification of the gear reduction train for a three hand wristwatch, i.e., having "seconds", "minutes", and "hours" hands.
A movement is described in U.S. Pat. No. 4,647,218 issued Mar. 3, 1987 to P. Wuthrich and assigned to the Applicant's assignee, wherein a stepping motor rotor with a Pinion consisting of two parallel pins equidistant from the rotor axis directly drives the "minutes" wheel of a two hand watch by stepping the rotor one half a revolution once each minute. The movement includes a wheel and pinion reduction gear rotatably mounted on a single shaft to drive the hours wheel and hours hand. However, this timepiece does not have a "seconds" hand.
A three hand wristwatch movement is disclosed in U.S. Pat. Nos. 4,426,158 issued Jan. 17, 1984 and 4,483,627 issued Nov. 20, 1984 to Muller et al., which incorporates a stepping motor rotor having a similar two-pin pinion driving a seconds wheel and seconds spindle. Coaxially disposed around a post supporting the seconds spindle from the stepping motor stator are two rotatable sleeves with connected wheels, one for the minutes and the other for the hours. A pair of wheel and pinion reduction gear assemblies are coaxially mounted to rotate with respect to one another and with respect to the stationary bearing support. One such wheel and pinion reduces the speed to drive the minutes wheel. The other wheel and pinion is driven by a pinion on the minutes spindle and reduces speed further to drive the hours wheel. This construction requires a pair of coaxially mounted reduction gear assemblies which are rotatable with respect to one another as well as with respect to the stationary bearing support.
Accordingly, one object of the present invention is to provide an improved movement for a three hand timepiece with simpler construction and fewer parts in order to reduce the cost.
Another object of the invention is to provide an improved movement for a three hand quartz analog wristwatch.